Conventionally, for example, a technique of pasting a hologram on a surface of an article or a technique of applying special ink on a surface of an article have been known as methods for anti-falsification of articles such as cards and security notes. In a technique in which the hologram is used, the authenticity of the article on which the hologram is pasted is determined by viewing the hologram, which appears to be three-dimensional or varies in color depending on the viewing angle. In a technique in which the special ink is used, for example, fluorescent ink or magnetic ink may be used as the special ink. The authenticity of the article on which the above ink is applied is determined by sensing information hidden in the above ink by irradiating ultraviolet light thereon or by magnetic sensors although the above ink may be viewed in the same manner as normal inks.
However, the above falsification techniques have become more sophisticated as hologram manufacturing techniques have come into wide use, it is easy to falsify the hologram, and the falsified hologram cannot thereby be distinguished from an authentic one. In addition, since it is easy to obtain inks similar to the fluorescent ink or the magnetic ink, it is easy to falsify the ink, and a device for sensing information hidden in the above ink is very large and requires a power supply. Due to this, it is difficult to employ the technique using the above ink.
A technique in which a seal having a reflecting layer composed of a cholesteric liquid crystal is adhered on an article is disclosed in Japanese Unexamined Patent Application Publication No. 4-144796. The cholesteric liquid crystal has a circular polarization light selectivity, has metallic luster, and varies in color depending on the viewing angle (blue shift), and is thereby anticipated as a medium for distinguishing articles. However, in the conventional technique, the entire medium is composed of the cholesteric liquid crystal and equally thereby exhibits blue shift. Due to this, there is nothing therearound which the medium of the cholesteric liquid crystal may be compared therewith in color, and only sensory judgment of the authenticity of the article can thereby be performed, and it is thereby difficult to distinguish. As a result, it is difficult to reliably confirm the authenticity of an article by simply viewing the article from one direction. In addition, since the entire discrimination medium is composed of the cholesteric liquid crystal, the manufacturing cost is greatly increased. Alternatively, there is a case of pasting a seal on a package in which articles such as goods are packed. However, if packages discarded by a user are stolen, falsified goods packed in the stolen packages may be sold, or if a seal is peeled off from a package, falsified goods packed in another package on which the stolen seal is pasted may be sold.
Therefore, objects of the present invention are to provide a discrimination medium which can prevent falsification, facilitates determining the authenticity of the articles reliably and enables reduction in the manufacturing cost, and to provide a discrimination method using the same.